Assembly of stylet and catheter

ABSTRACT

A grooved stylet having a puncture point aligned with the stylet axis is mounted through a catheter to form an assembly. The aligned puncture point enables more accurate piercing of a vein, and reduces the possibility of double piercing the vein. 
     The stylet near its proximal end is provided with a circular shoulder which abuts the proximal end of the catheter, and the catheter end is positioned on the stylet so that only the stylet puncture point projects beyond the catheter. 
     The catheter is constructed of a hydrophilic polymer which expands away from the stylet and permits the stylet to be withdrawn from the puncture site, leaving the catheter in place in the vein.

BACKGROUND OF THE INVENTION

This invention relates to a new and improved assembly for insertion of a catheter into a patient. More specifically, this invention relates to a stylet providing an axially aligned puncture tip, the stylet being inserted through a catheter to form an assembly which can effectively pierce a vein. Upon withdrawal of the stylet, the catheter remains in place in the vein.

Presently manufactured hypodermic needles, cannula, and other needles employ a ground needle tip having an off-axis alignment from the longitudinal needle axis. This enables a relatively even needle tip bevel to be formed. These off-axis tips present a problem in that insertion of the needle into the vein of a patient or user must be in an off-axis alignment mode, and this can lead to the needle double penetrating the wall of a vein. This is due to the inherent longer length of the needle tip beyond the catheter.

Another problem of employing a hollow needle with a catheter inserted therein is that upon insertion into a vein, there exists the possibility of the catheter double puncturing the vein.

Another problem associated in using a cannula or hypodermic needle is the necessity to manufacture the central bore of the needle, and in an accurate manner.

Another problem with prior art needles and cannula is that flashback of blood into the needle is not observed until the blood reaches the distal end or hub portion of the needle.

It would be preferable to provide an assembly including a catheter and vein piercing device such that flashback is observed almost immediately, i.e., near the puncture tip rather than at the distal end, or hub of the assembly.

It would be also preferred to form a puncture tip that not only has an even bevel, but in which the tip is axially aligned with the central longitudinal axis of the vein piercing device and the catheter. This longitudinal alignment reduces the possibility of double puncturing the vein.

Another problem with prior art needles is due to coring, and can result in blockage of a needle, or subsequent embolism in a vein, artery, etc. It would be preferred to manufacture a vein piercing device that does not require formation of a hollow bore, and thereby would eliminate the possibility of coring.

Furthermore, it would be desireable to manufacture a vein piercing assembly that minimizes or reduces the possibility of double puncturing a vein or artery by minimizing the amount of exposed puncturing tip in front of the catheter.

Present over-the-needle catheters have at least two problems: i. they have a proximal end shoulder, which makes it difficult to insert the catheter into a vein; and, ii. the catheters remain stiff when in place in the vein, and this causes patient trauma. It would be desireable to manufacture a vein piercing assembly in which the vein piercing element is adapted to easily pierce the vein and then be removed, leaving behind a soft associated catheter in the vein, with reduced trauma.

THE INVENTION

According to the invention, there is provided a vein piercing assembly of a catheter and inserted stylet. Since the stylet is solid, it can be formed at one end into a puncture tip having a uniform bevel, while at the same time being aligned with the central longitudinal axis of the stylet. This enables the stylet to be inserted into the vein, with the tip being aligned to the central axis of the stylet, rather than being off-aligned to the central axis. Furthermore, the stylet may be provided with an external longitudinal notch or notches, groove, flatspot, etc., which form a space between the stylet and external catheter. Flashback occurs along this longitudinal notch and can be seen immediately when it occurs, and this enables the user to immediately determine when the vein has been pierced.

The catheter is manufactured from a hydrophilic polymer which expands when it contacts blood in the vein. During expansion of the catheter, the stylet can be retracted leaving the catheter in place. The catheter then further expands along its axis when fluid from the attached intravenous administration solution is fed from a fluid container and a plastic I.V. set through the expandable catheter to the patient's system. Upon expansion, the hydrophilic polymer becomes soft, with a durometer hardness less than about 60 Shore; this tends to reduce trauma in the vein.

The assembly of this invention enables a reduction of about 30%-60% in puncture tip length, compared to conventional needle tips. Thus, for a stylet length of about 1"-6", puncture tips will correspondingly vary in the order of about 0.04"-0.12".

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side elevation in axial section of the assembly of a stylet and catheter according to the invention;

FIG. 2 is a sectional side elevation in axial section of another embodiment of the catheter and stylet assembly of this invention;

FIG. 3 is a sectional side elevation in axial section of an embodiment of the invention showing a grooved stylet;

FIG. 4 is a sectional side elevation in axial section of the stylet showing different embodiments of the stylet and catheter;

FIGS. 5-8 are sectional views in end elevation showing various forms of recesses or grooves along the stylet axis;

FIG. 9 is a sectional view in end elevation showing another embodiment of a catheter for the stylet; and,

FIG. 10 is a sectional view in side elevation showing the simultaneous machining of a stylet and catheter to produce an assembly having a uniformly curved surface between the catheter and the stylet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The catheter and stylet assembly 10 of this invention is shown in FIGS. 1, 2, 4, 6 and 9, and includes a configured stylet 11 over which is positioned a contoured catheter 12. The stylet is solid and may be manufactured of a stainless steel such as 304-316; typically, a stainless steel such as 304 may be used. Harder materials such as tungsten are also suitable, and possibly carbon fiber, alone or reinforced with resin. The stylet 11 includes a distal end 13, a rounded proximal end 14 having a vein or artery piercing tip 15, and a forwardly inclined circumferential shoulder 16.

The catheter 12 at its proximal end 12a, abuts the shoulder 16 and is restrained thereby from further movement towards the piercing tip 15. In addition, the catheter wall thickness is sized, and the catheter itself is shaped to define an overall continuous and uniformly curved outer surface 16 extending from the distal end 17 of the catheter to the rounded proximal end 14 and tip 15. Also, the interface 20 at the stylet shoulder 16 and the outer surface 18 of the catheter is essentially smooth.

The catheter is constructed of a hydrophilic polymer which expands upon contact with water. Publications disclosing hydrophilic polymers include: U.S. Pat. Nos. 3,822,238; 3,975,350; 4,156,066; 4,156,067; 4,255,550; 4,408,023; 4,424,305; 4,439,583; 4,439,584; 4,439,554; and, 4,439,558.

Typical bore sizes of the catheter vary from about 36 gauge and larger; wall thicknesses are designed to minimize kinking and may be derived from known formulae.

As shown in FIGS. 3, 4, and 5-7, the stylet may be provided with a groove to produce flashback when the stylet is inserted into a vein, artery, organ, or the like. FIGS. 1 and 2 show embodiments of the assembly which do not use a flashback groove.

As shown in FIG. 3, a stylet 25 provides a groove 26 which extends from the distal end 27 through a catheter retaining shoulder 28, at the proximal end 29, and which terminates near the tip 30.

FIGS. 5-8 illustrate various tupes of groove configurations that may be used for the stylet. In FIG. 5, a stylet 35 is shown with a V-notch shaped groove 36. A U-shaped groove 40 and octagonally shaped tip 40a are employed for the stylet 41 in FIG. 6, and a catheter 42 is positioned around the periphery of the stylet. If desired, the tip and catheter are ground together during manufacturing. Consequently, when blood flashes back along the groove after insertion of the stylet into a vein or artery, it will be contained within the groove by the catheter. Also, since the catheter is transparent or partially transparent, this flashback will be observable immediately, and will enable the user to determine that the patient's (or user's ) vein has been penetrated.

In FIG. 7, the stylet 50 provides a flat portion 51 which functions in the same manner as V or U-shaped grooves. As in FIG. 6, when the stylet is surrounded by a catheter, flashback blood will both be contained by the catheter and will be observable immediately upon penetration into the vein.

FIG. 8 shows a stylet 52 having a plurality of grooves 53 disposed at about 90° around the periphery of the stylet. For an outside stylet diameter of about 0.017", and with four grooves at 90° to each other, each triangular groove is sized about 0.004" at the base, and 0.003" deep.

FIGS. 2, 4 and 9 illustrate different types of catheters which may be utilized with a stylet. In FIG. 2, a stylet 55 is shown that is insertably mounted within a catheter 56. The longitudinal flashback groove is absent from this embodiment. A forward shoulder 55a near the proximal end of the stylet is much shallower than the corresponding shoulders in FIGS. 1 and 3. Hence, the proximal end 57 of the catheter will have a very small wall thickness in order to maintain a uniform curvature along the outer sidewall 58 of the catheter and the proximal end exterior surface 59.

In FIG. 4, the stylet 60 employs a flashback groove 61, and the circular retaining shoulder 62 at the proximal end 63 is inclined backwardly. This results in the catheter 64 becoming outwardly stressed, or buckled, at its proximal end 65.

FIG. 9 illustrates a stylet 68 similar to that of FIGS. 1 and 2 i.e., having no groove. A catheter 69 surrounds the stylet, and provides a plurality of inner grooves 70 along which blood flashback occurs. This construction is less expensive than machining a metal stylet since the grooves 70 can be formed by a plastic extrusion process rather than an expensive metal grooving process.

FIG. 10 shows a manufacturing process using a grinding wheel, a portion 75 of which is shown, to form a stylet puncture tip 76 and simultaneously configure the proximal end 77 of a catheter 78. The grinding wheel produces a uniformly curved puncture tip surface 79, 80 along the leading edge of the catheter and the stylet tip, respectively. No discontinuity occurs at the junction 81 between the inner wall of the catheter and the stylet. Consequently, insertion of the catheter into a vein is not impeded by the presence of a proximal catheter shoulder.

In operation, the stylet and catheter are inserted into a vein, artery, organ, or the like. If the catheter is to remain in place in the vein when the stylet is withdrawn, the proximal end of the catheter must be dislodged from the position against the proximal shoulder of the stylet when the stylet tip is still located in the vein. As previously indicated, a hydrophilic polymer is used as the material of construction of the catheter. Consequently, when the stylet is inserted into the vein, contact of the catheter with blood will cause the catheter tip to expand out of contact from the shoulder of the stylet. When the stylet is retracted, the catheter will remain in place in the user's vein.

Thus, the assembly of this invention provides a catheter which becomes relatively soft and flexible compared to prior art over-the-needle catheters, and reduces trauma when in the vein. Also, the present invention minimizes problems of entering the end of the catheter into the vein. 

I claim:
 1. An assembly for piercing a vein, artery, organ, and the like, comprising:a. a stylet defining an outer surface, distal end, proximal end, and a central longitudinal axis; b. a puncture tip formed at the proximal end of the stylet; c. a circumferential shoulder defined near the proximal end, and adjacent the puncture tip; and, d. a catheter comprising a hydrophilic polymer disposed over the stylet, the catheter defining an outer surface, a distal end, and a proximal end in contact with the shoulder of the stylet, and forming a continuous interface at the shoulder and outer surface of the stylet, thereby enabling the catheter to enter a puncture site without blockage at the proximal end, and upon contact with liquid in the puncture site, the catheter will expand and thus enable the stylet to be withdrawn, leaving the catheter in place in the puncture site.
 2. The assembly of claim 1, in which a longitudinal groove is defined on the outer surface stylet extending from a location near the puncture tip, and the catheter is transparent or partially transparent, thereby enabling flashback along the groove to be observed upon entry into a puncture site.
 3. The assembly of claim 1, in which the outer surfaces of the stylet and catheter are uniformly curved at the interface.
 4. The assembly of claim 1, in which the puncture tip is aligned with the longitudinal axis of the stylet.
 5. The assembly of claim 1, in which the catheter provides a hardness of less than about Shore 60 after contact with liquid in the puncture site.
 6. The assembly of claim 1, in which the puncture tip and proximal end of the catheter from a uniformly curved, continuous puncture tip surface.
 7. The assembly of claim 6, in which the puncture tip surface is formed by simultaneously grinding the proximal ends of the catheter and stylet.
 8. The assembly of claim 1, in which the circumferential shoulder of the stylet is inclined backwardly, and the catheter at its proximal end is outwardly stressed, or buckled at the shoulder.
 9. The assembly of claim 1, in which the bore sizes exceed about 36 gauge.
 10. A method of inserting an assembly of an over-the-stylet catheter into a puncture site in a vein, artery or the like, without coring, comprising:A. inserting the assembly into the puncture site, the assembly comprising: a. a stylet defining an outer surface, distal end, proximal end, and a central longitudinal axis; b. a puncture tip formed at the proximal end of the stylet; c. a circumferential shoulder defined near the proximal end, and adjacent the puncture tip; and, d. a catheter comprising a hydrophilic polymer disposed over the stylet, the catheter defining an outer surface, a distal end, and a proximal end in contact with the shoulder of the stylet, and forming a continuous interface at the shoulder and outer surface of the stylet, thereby enabling the catheter to enter the puncture site without blockage at the proximal end; B. contacting liquid in the puncture site with the assembly, the catheter being adapted to expand away from the stylet upon contact with the liquid; and, C. withdrawing the stylet, leaving the catheter in place in the puncture site.
 11. The method of claim 10, in which a longitudinal groove is defined on the outer surface of the stylet extending from a location near the puncture tip, and the catheter is transparent or partially transparent, thereby enabling flashback along the groove to be obsered upon entry into a puncture site.
 12. The method of claim 10, in which the puncture tip is aligned with the longitudinal axis of the stylet.
 13. The method of claim 10, in which the puncture tip and proximal end of the catheter form a uniformly curved, continuous puncture tip surface.
 14. The method of claim 10, comprising contacting liquid in the puncture site, thereby imparting a hardness of less than about Shore 60 to the catheter. 